My ex lost most of his flock (8 out of 10 hens) to his neighbor's dog. In the state of Ct, if an animal is threatening your livestock you have a right to defend your livestock... He was nice about it; ended up walking the dog home, feather's still in its mouth, and telling the lady that he'd lost 8 birds to the dog and if it showed up once more he was going to shoot it. The lady argued that it wasn't her dog, until her kid ran up and face planted on the dog who started licking the kid.... After that, the dog never showed up again.
I'd be most worried about that dog, as it apparently doesn't have any respect for your dogs. I'd also be concerned about rabies, if the dog is lose constantly. Animal control would be involved, especially if it'd come after me and mine. I'd also have checked the laws in your area and if legal, let them know you're going to shoot it if it shows up again. You don't even have to own a gun, tell them you do and that may be enough to take care of the problem. Otherwise, animal control.
Otherwise, I only free range mine about an hour before they would take themselves to bed. We have all manner of predators here, I even woke up to Great Horned owls outside my window once. And my dog views chickens as running squeaky toys... so I only let them out when they can be supervised.